LeetCode之First Unique Character in a String

s = "leetcode"
return 0.
s = "loveleetcode",
return 2.

public class Solution {
    public int firstUniqChar(String s) {
    if (s == null || s.length() == 0) {
      return -1;
    }
    HashMap<Character, Integer> map = new HashMap<Character, Integer>();
    for (int i = 0; i < s.length(); i++) {
      Integer in = map.get(s.charAt(i));
      if (in == null) 
        map.put(s.charAt(i), 1);
      else
        map.put(s.charAt(i), 2);
    }
    for (int i = 0; i < s.length(); i++) {
      if(map.get(s.charAt(i)) == 2) {
        continue;
      } else {
        if (map.get(s.charAt(i)) == 1) {
          return i;
        }
      }
    } 
    return -1;
  }
}